Environmental impact of trawling on the seabed: A review

Abstract

Fishers have been complaining about the effects of bottom trawl gear on the marine environment since at least the 14th century. Trawl gear affects the environment in both direct and indirect ways. Direct effects include scraping and ploughing of the substrate, sediment resuspension, destruction of benthos, and dumping of processing waste. Indirect effects include post-fishing mortality and long-term trawl-induced changes to the benthos. There are few conclusive studies linking trawling to observed environmental changes since it is difficult to isolate the cause. However, permanent faunal changes brought about by trawling have been recorded. Research has established that the degree of environmental perturbation from bottom trawling activities is related to the weight of the gear on the seabed, the towing speed, the nature of the bottom sediments, and the strength of the tides and currents. The greater the frequency of gear impact on an area, the greater the likelihood of permanent change. In deeper water where the fauna is less adapted to changes in sediment regimes and disturbance from storm events, the effects of gear take longer to disappear. Studies indicate that in deep water (>1000 m), the recovery time is probably measured in decades.

Seamount benthic macrofauna off southern Tasmania: community structure and impacts of trawling

“…Hutchings 1990, Jones 1992, Auster et al 1996, Collie et al 1997, Jennings & Kaiser 1998. These studies have demonstrated a variety of trawling impacts: direct impacts on the benthic fauna and substrate, and secondary impacts, particularly on fishes, arising from reduced cover and habitat complexity.…”

“…A rapidly growing literature has shown that trawling may substantially alter marine benthic habitats and communities (Bradstock & Gordon 1983, de Groot 1984, Sainsbury 1988, Hutchings 1990, Jones 1992, Auster et al 1996, Collie et al 1997. Several studies have also demonstrated significant secondary, or indirect, impacts on elements of the community, such as juvenile or adult fishes, that utilize biogenic structures on the seafloor directly impacted by trawling (Bradstock & Gordon 1983, Sainsbury 1988.…”

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…Whilst the susceptibility of benthic communities and habitat integrity to perturbation associated with bottom fishing activity has long been established (Thrush and Dayton 2002;Jones 1992), evaluations of the longer term effects of restructured post-disturbance communities inhabiting altered sedimentary conditions on biogeochemical processes have been less prominent (Lambert et al 2014). Cohesive shelf sediments have been considered to be particularly important areas for biogeochemical activity owing to the presence of elevated concentrations of organic matter and living biomass, contributing an estimated 44% of global denitrification and [40% of total organic matter burial (Muller-Karger et al 2005;Seitzinger et al 2006;Middleburg and Levin 2009).…”

Geoquímica sedimentaria en áreas de pesca de arrastre y no arrastre de fondo en la costa de Sinaloa-Sonora, Golfo de California

“…Los arrastres de fondo marino con una zona de perturbación de 120-150 cm de ancho y una profundidad de 5 cm, ocasionan un detrimento de la biota marina (Jones, 1992;Engel y Kvitek, 1998;Hall, 1999) afectando directamente la abundancia e indirectamente las estructuras y organismos que sirven de hábitat y alimentación, respectivamente (Sainsbury, 1988;Hall, 1999). A pesar de estas preocupaciones, la intensidad y eficacia de la pesca de arrastre de fondo han aumentado en todo el mundo (Hall, 1999).…”

“…Los estudios realizados sobre el impacto de la pesca de arrastre en los diversos componentes del ecosistema marino, han encontrado resultados mixtos y con ello se demuestra que los efectos de la pesca de arrastre sobre el bentos no es una tarea fácil de investigar por razones diversas. Los daños causados en el ecosistema marino varían en función del sistema de pesca de arrastre, las artes (tipo, configuración y peso), el tipo de sedimento y biota, y las perturbaciones naturales (Jones, 1992;Kaiser y Spencer, 1996).…”